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Figure 3 | Microbial Cell Factories

Figure 3

From: Protein folding and conformational stress in microbial cells producing recombinant proteins: a host comparative overview

Figure 3

Schematic representation of protein folding and aggregation in recombinant E. coli. After de novo synthesis, a fraction of recombinant proteins (especially heterologous proteins with conformationally complex disulfide bridges) do not reach their native conformation and aggregate as insoluble deposits named inclusion bodies. Protein aggregates already exist in the soluble cell fraction, and can involve native or quasi-native protein species. The main cytoplasmic chaperones involved in the protein folding process (red arrows) include the trigger factor, DnaK, DnaJ, GrpE, GroEL and GroES. Both soluble aggregates and individual protein species can enter the virtual insoluble cell fraction (indicated by a dashed line) and deposit as inclusion bodies, in a fully reversible process (green arrows). Protein release from inclusion bodies is mainly controlled by DnaK, ClpB and IbpA,B. Proteases (lon, ClpP and others) attack both soluble and insoluble species with folding defects. In particular, proteases degrade inclusion body proteins in situ, or through a more complex process intimately related to the protein release process, and therefore, strongly dependent on DnaK.

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